Copperplating of mirrors



I Ap 5,.1 44- w. OWEN 2,347,608 I COPPER PLATING OF MIRRORS Filed March. 8, 1941 4 Sheets-Sheet l nvviszv T02 W MLL/HM- Ou/E/V COPPER PLATING OF MIRRORS Filed March 8, 1941 4 Sheets-Sheet 3 197' Tox/vs v W. OWEN COPPER PLATING OF MIRRORS Apt i125, 1944.

Filed March 8, 1941 4 Sheets-Sheet 4 M/vE/v T02 ML L. IHM Owe/v Mews/3w 6' T Toe/var of silvered mirrors Patented Apr. 25, 1944 William Owen. Pittsburgh, 2a.,

burgh Plate Glass Company. All

assignmto Pittsegheny' County.

Pa., a corporation of Pennsylvania Application March 8, 1941, Serial No. 382,377 7 Claims. J (Cl. 204-225) The present invention relates to an apparatus designed for applying coatings of copper or similar substance susceptible of deposition as protective films upon a surface of a plate-like object and it has particular relation to the provision of an apparatus -for electrolytically coating the backs with a layer of metallic copper.

One object of the invention is to provide an apparatus for electrolytically coating mirrors with copper with a minimum amount of handling and minimum risk of mechanical injury to the silver A second object of the invention is to provide an apparatus of the foregoing type by use of which uniform films of sludge free copper are deposited with a minimum expenditure of electrical energy.

These and other objects of the invention will be apparent from consideration of the following specification and the appended claims.

It is well recognized in the art that the silver films of mirrors are sensitive to moisture and chemically active fumes and the like which are oftenpresent'in the atmosphere. In order to protect the films from the action of such agencies it is common practice to provide the silver film with a backing of relatively impermeable material, such as various paints, varnishes and the like. However, most satisfactory results have been obtained by electrolytically depositing a film of copper upon the silver.

Considerable difiiculty has been encountered in the copper plating of mirrorsand notably those of large size because they are difllcult to pick up and transport without exposing the relatively delicate silver film toscratching or abrasion. Furthermore, in the conventional types of apparatus there is a tendency for cdpper sludge to settle upon the mirror undergoing copper plating and thus produces imperfections in the operation. In some typesnf apparatus heretofore available for the operation, the spacing of the anode employed to transfer electric current to the solution of copper compound is not uniformly spaced from the'silver him and as aresult considerable variation in the resistance offered to electrolytic currents passing to various parts of the plates is encountered and this results in variations in the thickness of the copper plating deposited.

In accordance with the ent invention. it is proposed toovercome the foregoing difliculties by provision of a conveyor system comprising rollers adapted to move plates of glass in horizontal position into proximity to the platin apparatus and a copper plating rack formed provisions of the pres-' lift the plates of glass from the rollers to an almost vertical position and then to slide the rack into a plating bath, where the plating operation is performed with the glass disposed almost vertically and with the silver film in close and uniform I proximity to the anode designed to conduct electricityinto the bath.

For a better understanding of the invention reference may now be had to the accompanying drawings in which like numerals refer to like parts throughout.

In the drawings Figure l is a fragmentary view partially in elevation and partially in section of the apparatus employed, in effecting a plating operation;

Figure 2 is a sectional view taken substantially upon the line 11-11 of Figure l; I

Figure 3 is a fragmentary sectional view showing on a larger scale a latching mechanism employed to hold the rack structure in elevated position;

Figure 4 is a diagrammatic view showing the wiring of the apparatus employed to effect movement of the rackand the rack transporting mechanism in its transit from one position to another.

As shown in Figure 1, the apparatus includes a conveyor system 5 for conducting mirrors to the plating apparatus anda system i for conducting it away. Each system includes supporting side rails I for rollers l and columns 9 supporting the rails at an appropriate height above the floor.

The plating apparatus may embody a conveyor system designed to bridge between systems 5 and i and comprising side rails ll upon columns "a of channel section and a drain pan llb spanning the space between them. One rail bears a beam ll supporting bearings II at the ends of rollers ii of the system.- At the opposite ends the'rollers are journaled in bearing brackets ll. The firstmentioned ends, as shown in Figure 3,'are provided with sprockets I, which are engaged by and driven by a sprocket chain It. The chain is looped about suitable idler sprockets ll, which function to take up the slack in the chain and are journaled upon shafts ll, upon a bracket is, extending from one of the side bars ll. The end rollers are further provided with sprockets 20 about which are trained chains 2| that drive conveyor systems I and 6.

The conveyor system comprising rollers I3 is, disposed above a pit 22 which is in part closed or, so by a section of floor 23. Copper plating olution is contained in an open elongated tank or container, of section, which is disposed in position slightly inclined 'from the vertical and rests at its bottom upon suitable supports 25. The sides of the container are engaged by beams 2| which are designedto reinforce it a ainst the hydraulic pressureexerted therein. The beams at their upper extremities are supported by longitudinally-extending I beams 21, which also function as supports for the floor 22. An inverted channel 28 secured along one edge of the tanksupporte a bus bar '28 insulated or covered by a bar of wood, rubber or the like. The tank is lined'throughout with a layer ll of rubber or other nonconductive and relatively chemically-resistant material, and a similar coating 32 may be applied to pan llb, beams ll, II and any other parts that are exposed to plating liquor. The anode for the tank comprises a sheet or layer 3I of copper, which preferably is of substantially the same dimensions as one face ofthe tank and is Joined to bus bar 28.

Apparatus for transporting glass plates upon the conveyor system to the copper plating tank includes a'tiltable platform or table 250 including spaced bars 35, which at one extremity are rigidly secured to a horizontal shaft I6, disposed contiguous to the ends of the rollers l2 and the corresponding edge of tank 24 and which rotates in suitable bearings 21 upon the side bars ll.

in Fig. l of the drawings. The cables, after passing around the drums 84, are also trainedabout drums It, which are journaled upon a shaft H in the brackets 24.. The extremities of the cables are attached as indicated in broken line in Fig. 2 to the upper extremity of the glass rack.

Latch mechanism shown in Fig. 3 for holding the glass rack or carriage 40 in position upon the tiltable platform Ila includes a dog or a plurality of dogs 80, pivoted as indicated at 6| upon one or a plurality of the brackets 38. Each dog is provided with a hooked portion 62 adapted to engage with a peg or rod 82 projecting from the sides of the bars 42 of the rack. A tension spring 84 interconnecting the dog and any convenient fixed point of attachment, such as the shaft l1 of pulley 56 urges the dog toward the pin 63.

These bars have projecting end portions 36a of such length and so disposed that the upper edges thereof align with the rear face of tank 24, When the platform is raised, thus providing a continuous track way from the platform into the bath, each of the bars is designed to rest between a pair of contiguous rollers I! at a slight distance below the upper portions of the latter. In order to interconnect the bars at their free extremities they are provided with upwardly-extending brackets as (best shown in Figs. 2 and 3), which further have ansularly disposed portions 39 interconnected by a horizontal bar 4 l, g

A rack 40 for supporting the glass during the plating operation includes bars 42 so spaced as to rest between the rollers l3 whenpthey are in horizontal position and being provided at their extremitles contiguous to brackets 38 with brackets 43 (best shown in Fig. 3), which are interconnected by a bar 44. The opposite extremities of the bars are interconnected by the transverse bar 46. Certain of the bars 42 are provided with rollers 41, designed to travel upon the bars II of the tiltable platform and the inner face of tank 24. The bars are alsoprovided at appro-.-

priate points adjacent to the edge of the rack I platform is shown in an*automatic brake indicated as a unit at 48.

This'mechanism secured to a beam 50, which along with beam Ila is disposed transversely of beams lb, includes driving shafts ll upon which are keyed winding drums I2, about which are trained cables II that are further trained about drums I4 suitably iournaled in brackets 55 upon the beam'lta. As many drums as may be desired are provided, for example, for purposes of illustration; four are included, as shown It is also to be noted that the dog has a projecting arm 66, which when'the platform is in its lowermost position engages rail ii of the conveyor system, thus to release the dog from the pin at the lowermost position of travel of the glass supporting platform,

A spring 84 of inverted U-shape is secured at one extremity, to the bar 4| and at the opposite extremity projects downwardly to engage bar 44 of the glass supporting rack. It will be apparent that with the dog engaging the pin 63 the spring is held slightly flexed. Whenthe platform is horizontal the hook 62 is released and the glass rack is pushed by the spring transversely of the trackwayor conveyorsystem. The pins engaging the edges of the glass are thus released from their contact with the glass, leaving the latter free to move under the urge of the rollers of the conveyor system.

Mechanism to check of the glass supporting platform, without undue shockjas it is lowered from its elevated to its horizontal position, includes a builer device 89, best shown in Fig. 3. The device includes a vertically disposed tubular member H, which at its lower extremity is secured to a support, such as a portion 12 of the building floor. This tubular member includes a helical spring 13, which at its upper extremity bears against a lower end of a plunger 14, that projects at its upper extremity from the tubularmember, and is adapted to engage a lug or arm 15 upon bar 4|.

It is further to be noted that a limit switch 18 having arm 11 is secured to any suitable support, e. g. bracket is upon member '|.I in position to be engaged by a cam is carried by the bar 4i. This switch is so connected into the circuit (to be later described) of the motor 40 as to stop the rotation of the latter when the platform has reached its lowermost or horizontal position.

A builer to check the upward movement of the zontal rod 80, sliding horizontally in bracket 5| upon the beam "a and being provided at one extremity ith locked nuts 82 designed to prevent displacement of the rod from position, At the opposite extremity the rod is provided with a rigidly attached buffer-head 22-, which is urged forwardly toward the bar 4| when the platform is in elevated position by means of a helical spring 44 coiled about the rod and at one extremity with one side of the bracket II, and at the opposite extremity engaging with the member ll.

A latch mechanism L for holding the platform in approximately vertical position includes spacedlatching rods It rigidly secured upon arms 81, which are pivoted at Ila. At their the downward movement' Fig. 2 and includes a horilower ends the rods are provided with rollers 88 designed to engage and hold the bar 4I. At their .upper extremities the rods are connected by links 89 pivoted to operating levers 90, which are rigidly secured upon a shaft 8| journaled in bearings 92 upon the beam 50a. The opposite extremity of one of the end levers is.provided with a pull cord 93, by means of which the lever may be operated to raise the arms 86 and release bar III. After release of the bar the platform may be lowered to its original horizontal position by reversal of the motor 48.

It is to be observed that the arm 66 of the latch dog 60 also includes an angularly directed portion 94 disposed to be engaged by the roller 88 when the platform approaches its upward limited travel. In this way the dog 60 is actu-' ated to release the pin 63. With the pin released the glass rack or carriage may be lowered along the trackway provided by the arms of the platform, in order to introduce the rack and the glass carrier thereby into the bath in the plating tank.

The movement of the tiltable platform to its uppermost position also operates a limit switch I indicated diagrammatically in Fig. 4. This switch includes an operating arm IOI carrying a roller I02, which is engaged by a suitable camlike shoe I03 upon the glass rack. The switch, like the switch 16, already described, is so connected into the circuit of the motor 49 that opening thereof is effective to open the circuit of the motor and thus to stop it.

A third limit switch I04 is disposed adjacent to the upper extremity of the plating tank and includes an operating arm I06 also engaged by the shoe I03. This switch, like the switch I00, is connected into the circuit of the motor 49 for purposes of stopping the latter when the glass-carrying rack 40 has been introduced into a plating bath. In order to start the motor after it has been stopped by operation of one of the switches 16, I00, or I04, suitable double circuit push-button switches I01 and I08 are provided.

The operating circuits in which switches 16,

I00, I04 and the controlling switches I01 and I08 are connected will now be described. These circuits include an up" switch mechanism H0 and a down switch mechanism III. Switch IIO includes a movable member II2 carrying cross arms or connectors II3, II4,, H6 and H1, which respectively bridge the gap between pairs of contact points H8, H9, I2I and I22. The down switch III is similar in all details and the parts thereof have been indicated by the same numerals, but with prime marks applied for purposes of identification. Conductors I connect upperp'oints H8, H8 and I2I respectively to upper points I2I, H9 and H8 of-the down switch III, and conductors I interconnect points II8-II8', ,II3-II9' and I2I-I2I. Bus lines I23, I24 and I26 are respectively connected to the upper of each of the pairs of points I2I, H9 and H8 of switch H0, and lines I21, I28 and I20 from the corresponding lower points lead to themotor at 48.

It is to be observed that the two switches H0 and III are provided with holding coils I3I and I32, which are provided with armatures or plungers l3l, I32, having suitable mechanical connections (indicated merely diagrammatically) with the elements II: and 2'. They are further mechanically interlocked as indicated by broken lines A so that when'one switch is closed the other must be open. In Figure 4 the interconnected elements H0 and III are shown in an intermediate or neutral position in which both switches are open. This position of course isheld only momentarily while one switch is being opened and the other closed. The circuit of coil I3I includes conductors I33 and I33a,

the latter of which is attached at one extremity to the point II9 connected to bus bar I24. It may, also, be provided with a normally closed switch I33b, At its opposite extremity the coil second upper point I44a. of switch I45 in turn is connected by lead I46 to the upper contact point I2I and the power line I23, thus ,providing a complete circuit through the holding coil I3I when the button of the switch I01 is depressed.

In order tomaintain the circuit in the holding coil'after the button of switch I01 is released, a lead I41 from the point I31 is connected to the lower of the points I22 while the upper of the points I22 is connected by line I48 to pointv I39a of switch I01. Points I39a and H211 of switches I01 and I08 are interconnected by line A circuit from bus line I24, to energize the coil I3I, is established when the button of switch I01 is depressed through lines I33a, I33, 434, switch I00, lines I36 and I38, switch points I39 and I39a, line I50, switch I08, line I43, switch I45 and line I46 to bus line I23. Thus when'thc coil is energized to close the switch IIO a circuit is established from line I23 throughthe line I46, switch I45, line I43, switch I08, line I50, line I48, arm II1, line I41, line I36, switch I00 and line I34 to the coil I3I and from the latter through line I33, I33a, to'bus I24. The circuit is thus maintained by the holding coil and the motor unit 40 is actuated by current flowing through arms H3, H4 and H6 to line I21, .I28 and I29 until the switch I00 is operated by the cam I02 to break the circuit. Downward movement of the tiltable platform from tilted to horizo'ntal position and also of the glass carrying car into the plating bath is effected by means of the switchmechanism III.

The lower pair of contact points I53 and I53a of switch I08 are connected by line I53b to upper point I40a of switch I01. Point I40a is further joined by line 01) to the upper of points I22 in switch III. The point I53a is in series through line I54 with the holding coil I32, which in turn is further in series throu h line I55 with limit switch I04 connected by line I51 to limit switch 16. Switch 16 is also Joined by lines-I58 and I33 to contact point 'I I8 and thus to bus line I24.

Assuming that the tiltable platform is in elevated position and the glass-carrying rack is retracted from the plating bath, both of the switches 16 and I06.will be closed and limit switch I00 will be open. If the button of switch I08 is pressed current will then,,fiow from the bus line I23,

through line I46, switch I45, line I43, line I,

switch I01, line I531), lines I54, switch I04, line I51, switch 16, lines I58 and I331: to bus I24, to-

energize coil I32 and close switch I I I.

when the button switch is released, a holding "down switch III is roller I51 operating in guides (not shown).

down switch I I I circuit is established from bus I23 through line I43, switch I45, lines I43 and I, through switch I01, line I401 arm II'I, coil I32, line I55, switch I04, line I51, switch 15, lines I58 and I330 to bus bar I24.

Assuming that the switch H is closed in order to wind up the cable 53, current from bus lines I23, I24 and I25 will flow through arms H5, H4, and H3 respectively, to lines I29, I28 and I21, to motor 49, to activate the latter. The platform 35a may thus be elevated from horizontal to inclined position. The rack 40, when in the bath, may also be lifted from the bath by the same winding operation, when the platform is in elevated position. If the up" switch I I0 is open and closed current flows from bus lines I23, I24 and I28 through lines I20 respectively, through arms H3, H4 and H3 to lines I25 and through lines I21, I23 and I20, to cause motor 49 to run in the desired direction to unwind the cable 53.

Manifestly, during movement of the rack to or from the bath, the platform 35a must be held in tilted position by latch mechanism L. This latch is operated by hand pull 93 to permit the platform to be lowered to horizontal position.

Stoppage of unit 49 may be effected at any point in the cycle of operation merely by pressing switch I45 to open the circuit of lines Band I43.

An electrical conductor system for supplying current to the silver films upon mirrors to be plated includes a flexible strap I55, of superposed thin, flexible plates of copper or the like. This strap is joined at one end to a bus I55 of a source of current. It is also looped about a take-up At its opposite end the strap is attached, as shown in Fig. 3, to bus bar I58 upon bar 44. The bus bar, in turn, is provided, as shown in Fig. 1, with spaced flexible connectors I59, which are equipped at their extremities with clips I'll, designed to be clipped upon the edges of the glass to establish contact with the silver film.

In the operation of the apparatus, the mirrors, to be plated, are conveyed by the rollers of conveyor 5 to rollers I3 of the plating apparatus. It is to be understood that during this operation the bars 35 of platform 35a and bars 42 of rack 40 recline between rollers I3. When the blanks are above the rack, the rollers 01' the entire system are stopped and clips III are attached to the glass. The button switch I01 is then operated to close up switch" I01, and operate motor 49 to take up cables 53 and lift platform 35a. When the platform reaches its uppermost position, latch L engages bar 4I. Also, limit switch I00 is operated to stop unit 49, and hook B2 is from pin 63. Likewise, springs 84 are compressed and held so long as latches L operate. To lower rack 40 into the bath, button switch I08 is operated to close down switch III, thus causing motor 40 to reverse and play out cable 53. Downward movement of the rack is stopped when the cam I03, on the rack, engageslimit switch I04. The rack remains in the bath until the film of copper upon the mirror is sufficiently thick; then switch I0! is again operated to close up" switch H0. The cable 53 winds up until cam I03 again engages switch, I04 to stop the, motor. Upon release of latches L the springs 84 initiate downward movement of the platform 35a, thus releasing cam I03 from the limit switch I00. Buttonswitch may, subsequently be pressed to close disengaged The platform descends to horizontal position in which the copper-plated mirrors rest upon rollers I3. Dog 50 then engages rail I I to release rack 40 and simultaneously limit switch It is opened to stop motor 43. The motor normally rotates for a moment after the switch opens. This overtravei is sufllcient to create a slight slack in cable 53, so that when the rack is released, it is kicked" transversely by spring 33 a sumcient distance to release pegs 43 from the edges of the mirrors. The conveyor rollers I3 and 3 may then be started to carry them away.

The form of the invention herein shown and described is merely exemplary. Numerous modiilcations may be made therein without departure from the spirit of the invention or the scope of theclaims.

What I claim is:

1. In an apparatus for coating plates, a tank having an inclined side wall providing a track within the tank, said tank being adapted to contain a coating medium, a platform Journaled to tilt from horizontal position to a position approximately aligning with said side wall about an axis contiguous to and parallel to an upper edge of the tank, a carriage mounted to move upon the platform and to rest upon it while it is in horizontal position, said carriage being designed to support the plates while they are being coated, means to tilt the platform about its axis from said reclining position to an inclined position and to move the carriage from the platform when the latter is tilted along said inclined side wall of the tank, then back to the platform, said apparatus including means to maintain the platform in inclined position while the carriage is being operated.

2. Apparatus as defined in claim 7 in which the connection for the plate is flexible, is joined to the carriage at one end and is provided with flexible leads having clips for engaging an edge of the plate.

3. In an apparatus for coating plates, a tank, a platform iournaled to tilt upwardly from a reciining position about an axis contiguous to an upper edge of the tank, a carriage mounted to move upon the platform and being designed to carry a plate to be coated, a sheave upon the swinging edge of the platform, a cable attached to the carriage and being passed about the sheave and further being trained about a winding drum for tilting a platform from a reclining position to an angularly upwardly inclined position and then for lowering the carriage into the tank, guide means in the tank to direct the movements of the carriage while it is therein, said uide means being aligned with the platform when the latter is in inclined position and a latch for locking the platform in upwardly inclined position while the carriage is being lowered into the tank.

4. Apparatus for electroplating plate-like bodies with a metal, said apparatus comprising a tank for a plating bath, a platform journaled at one edge. of the tank to swing from reclining position to a position in which its upper surface aligns with the adjacent surface of the tank, a movable carriage mounted to rest upon the platform in reclining position ind to travel with the platform when the latter is raised, and then to travel upon the contiguous side of the tank into and from the bath, means to tilt the platform about its axis and to move the carriage into and from the bath, said apparatus being provided with means to hold the platform in tilted position while the carriage is being manipulated, means to supply electrical current to a plate upon the carriage, the latter means comprising an anode of the metal with which the plates are to be coated, disposed within the tank in parallelism to a side of the plate to be coated, said anode being connected to one side of a source of plate current, a flexible conductor joined to said carriage and constituting the other conductor of said source of plate current, flexible conductors having clips adapted to engage an edge of the plate to be coated, joined to the latter conductor.

5. In an apparatus for electroplating the backs of mirror plates, a tank for an electroplating bath, a conveyor for plates comprising horizontal rollers disposed in parallelism to each other and being disposed to carry the plates alongside the tank, means to introduce the plates into the bath in an upwardly tilting position comprising a carriage constructed of bars adapted to nest between the rollers and to support a plate to be coated thereupon, means to tilt said carriage upwardly into an inclined position with the lower edge over the tank, means to slide the carriage while in inclined position downwardly into the tank and then to retract it to its starting position, a flexible electrical conductor secured to said carriage and providing means supplying electrical current thereto while it is in the tank and branch conductors secured to the first-mentioned conductor and having clips adapted to engage an edge of a plate upon said carriage, an anode in the tank contiguous to the faceof the plate and the second conductor joined to said anode.

6. An apparatus for electrolytically applying coatings to plates, said apparatus comprising a tank adapted to contain a solution of an electrolyte for the coating operation, the tank having a downwardly-inclined trackway disposed therein and extending below the surface of the I electrolyte, horizontal rollers adapted to support the plates to be coated preliminary to the coating operation, mounted along a side of but exterior of the tank contiguous to an upper edge thereof, a platform comprising bars adapted to nest between said rollers and being mounwd to tilt upwardly from reclining position in which the bars are nested between the rollers to a position approximately aligning with said trackway and providing an upwardly-extending extension 5 of the trackway, the tilting movement bein about an axis contiguous to the upper end of said trackway, a carriage upon the platform for supporting the plates to be coated and comprising spaced bars corresponding to the bars of the platform to nest between said rollers when the platform is in reclining position and when so nested being below the plates upon the rollers, means to swing the platform from reclining position to an upwardly tilted position, to lower the carriage along thetrackway with the plates thereon, into the tank while the platform is in tilted position and to return the carriage to the platform after the coating operation is completed, said apparatus including means to hold the platform in tilted position, the carriage being provided with a flexible electrical conductor for supplying electrical current, the conductor being connected to bran hes having contact with the plates to be coated.

7. Apparatus for electrolytically coating a mirror plate, comprising a deep upwardly-extending tank for a plating bath, an anode'plate disposed in downw -inclined position within the tank and adapted to be covered by the "bath, a carriage for supporting and moving a plate to be coated into the bath, said carriage being hingedly mounted totllt about an axis con tiguous to an'edge thereof and contiguous edge of the tank, from a horizontal position, for

a receiving a horizontally-disposed plate to be coated to an upwardly-inclined position parallel to said anode, means extending parallel to said anode for guiding the carriage into the bath with said plate parallel to the anode and with 4. the edge adjacent the axis disposed downwardly and actuating means for about its axis from one extreme position to the other, then lowering the carriage along said guideway into the bath, then finally retracting the carriage and returning itto its initial position and electrical connections for supplying electrical current to the plate and the anode. WIILIAM OWEN.

toan,

tilting the carriage 

